Liquid pharmaceutical preparations exist which contain insoluble or particulate constituents. This can be due to the insolubility of the drug in the vehicle in which it is stored. Alternatively, this can be due to the formulation of the drug to purposely render it relatively insoluble allowing the drug to be released over extended periods of time once it is injected. As a result, the insoluble or particulate constituents in the liquid pharmaceutical preparations separate upon storage, even over short periods of time.
In addition, these pharmaceutical preparations are typically packaged in cartridges or pre-filled syringes as the final drug container. There are a number of well known reasons for packaging the drugs in pre-filled syringes or cartridges ranging from economic efficiency to ease of use and administration. However, the inherent nature of these containers makes it difficult to resuspend the settled material since a cartridge or pre-filled syringe generally has a smaller volume of area in which to accomplish the resuspension than what one would normally find in a vial or ampule. As a result, the needle to be used for delivering the medication can become clogged if the suspensions are inadequately resuspended.
This potential for a clogged needle is particularly problematic in cases when the liquid pharmaceutical preparation containing insoluble particles is self administered or administered in the home by non-professional care givers. Ordinarily, when these liquid pharmaceutical preparations are administered in the hospital or other health care providing institutions by trained staff, one can rely on adequate handling of the medication despite settled material and plugged needles ensuring proper drug delivery. However when such pharmaceutical preparations are self administered or administered in the home by non-professional care givers, the risk for inadequate handling of the medication increases since the injection of such formulations requires that the administrator be able to adequately resuspend any settled material and clear the needle to ensure proper drug delivery.